Jason Wang
2021-Jun-29 03:29 UTC
[PATCH v8 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace
? 2021/6/29 ??10:26, Yongji Xie ??:> On Mon, Jun 28, 2021 at 12:40 PM Jason Wang <jasowang at redhat.com> wrote: >> >> ? 2021/6/25 ??12:19, Yongji Xie ??: >>>> 2b) for set_status(): simply relay the message to userspace, reply is no >>>> needed. Userspace will use a command to update the status when the >>>> datapath is stop. The the status could be fetched via get_stats(). >>>> >>>> 2b looks more spec complaint. >>>> >>> Looks good to me. And I think we can use the reply of the message to >>> update the status instead of introducing a new command. >>> >> Just notice this part in virtio_finalize_features(): >> >> virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK); >> status = dev->config->get_status(dev); >> if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) { >> >> So we no reply doesn't work for FEATURES_OK. >> >> So my understanding is: >> >> 1) We must not use noreply for set_status() >> 2) We can use noreply for get_status(), but it requires a new ioctl to >> update the status. >> >> So it looks to me we need synchronize for both get_status() and >> set_status(). >> > We should not send messages to userspace in the FEATURES_OK case. So > the synchronization is not necessary.As discussed previously, there could be a device that mandates some features (VIRTIO_F_RING_PACKED). So it can choose to not accept FEATURES_OK is packed virtqueue is not negotiated. In this case we need to relay the message to userspace. Thanks> > Thanks, > Yongji >